Angular Distribution of Photo-Neutrons from Deuterium

Abstract

A study has been made, using 2.76 Mev ${\mathrm{Na}}^{24}$ gamma-rays, of the angular distribution of photo-neutrons from deuterium under approximately ideal conditions of low neutron scattering from the general surroundings into the detector. Results were obtained for two general methods of neutron detection, a B${\mathrm{F}}_3$ chamber and the Szilard-Chalmers reaction on ${\mathrm{C}\mathrm{a}\left(\mathrm{M}\mathrm{n}{\mathrm{O}}_4\right)}_2$. Assuming the neutron distribution to have, in the barycentric system, the form $I\left(\theta \right)=a+b{sin}^2\theta$, the values of $\frac{a}{b}$ obtained are 0.212±0.008 for the first method and 0.203±0.040 for the second, giving as a weighted average 0.211±0.008. From this, the ratio of the photomagnetic cross section to the photoelectric cross section is calculated to be 0.317±0.012.